The present invention relates to the manufacture of plastic light-transmissible articles such as video discs, ophthalmic lenses, skylights and the like. The present invention relates in particular to light-transmissible articles including photochromic dyes and pigments.
It is known in the prior art to introduce organic molecules exhibiting photochromic properties into a number of light-transmissible articles including optical articles. Considerable effort has been expended in the prior art in finding means of applying these dyes to optical elements of varying section thickness, such as spectacle lenses. Available options for introducing dyes into the polymeric article are:
(1) Impregnation or imbibing from a fluid medium contacting the surface, PA1 (2) Incorporation of the dye in an optical coating resin applied to the lens surface(s); and PA1 (3) Impregnation or diffusive transfer from a solid or gel in contact with the polymer surface, PA1 (4) Dispersion of the dye in the monomer or thermoplastic from which the lens is to be fabricated. PA1 A. Spectacle lens with negative refractive power PA1 B. Spectacle lens with positive refractive power PA1 C. Lens as A, but having bifocal addition PA1 1,3-dihydrospiro2H-anthra2,3-d!imidazole-2,1'-cyclohexane!-5,10-dione PA1 1,3-dihydrospiro2H-anthra2,3-d!imidazole-2,1'-cyclohexane!-6,11-dione PA1 1,3-dihydro-4-(phenylthio)spiro2H-anthra'1,2-diimidazole-2,1'-cyclohexane! -6,11-dione PA1 1,3-dihydrospiro2-H-anthra1,2-dimidazole-2,1'-cycloheptane!-6,11 -dione PA1 1,3,3-trimethylspiro'indole-2,3'-3H!naphtho2,1-b!-1,4-oxazine! PA1 2-methyl-3,3'-spiro-bi-3H-naphtho2,1-bipyran! (2-Me) PA1 2-phenyl-3-methyl-7-methoxy-8'-nitrospiro4H-1-benzopyran-4,3'-3H!-naphtho !2,1-b!pyran PA1 Spiro2H-1-benzopyran-2,9'-xanthene! PA1 8-methoxy-1',3'-dimethylspiro(2H-1-benzopyran-2,2'-(1'H)-quinoline PA1 2,2'-Spiro-bi-2H-1-benzopyran! PA1 5'-amino-1',3',3'-trimethylspiro2H-1-benzopyran-2,2'-indoline PA1 Ethyl-.beta.-methyl-.beta.-(3',3'-dimethyl-6-nitrospiro(2H-1-benzopyran-2,2 '-indolin-1'-yl)-propenoate PA1 (1,3-propanediyl)bis3',3'-dimethyl-6-nitrospiro2H-1-benzopyran-2,2'-indol ine! PA1 3,3'-dimethyl-6-nitrospiro2H-1-benzopyrao-2,2'-benzoxazoline! PA1 6'-methylthio-3,3'-dimethyl-8-methoxy-6-nitrospiro2H-1-benzopyran-2,2'-ben zothiozoline! PA1 (1,2-ethanediyl)bis8-methoxy-3-methyl-6-nitrospiro2H-1 -benzopyran-2,2'-benzothiozoline!! PA1 N-N'-bis(3,3'-dimethyl-6-nitrospiro2H-1-benzopyran-2,2'(3'H)-benzothioazol -6'-yl)decanediamide! PA1 -.alpha.-(2,5-dimethyl-3-furyl)ethylidene(Z)-ethylidenesuccinic anhydride; .alpha.-(2,5-dimethyl-3-furyl)-.alpha.',.delta.-dimethylfulgide PA1 2,5-diphenyl-4-(2'-chlorophenyl)imidazole PA1 (2',4'-dinitrophenyl)methyl!-1H-benzimidazole PA1 N-N-diethyl-2-phenyl-2H-phenanthro9,10-d!imidazol-2-amine PA1 2-Nitro-3-aminofluoren PA1 2-amino-4-(2'-furanyl)-6H-1,3-thiazine-6-thione PA1 Ciba Geigy Tinuvin P-2(2'-hydroxy-5'-methyl-phenyl) benzotriazole! PA1 Cyanamid Cyasorb UV 531 -2-hydroxy-4-n-acetoxy benzophenome! PA1 Cyanamid Cyasorb UV 5411 -(2(2'-hydroxy-5-5-octylphenyl) benzotriazole! PA1 2(2'-hydroxy-3',6'(1,1-dimethylbenzylphenyl)benzotriazole PA1 2(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole PA1 bis2-hydroxy-5-methyl-3-(benzotriazole-2-yl)phenyl!-methane PA1 bis2-hydroxy-5-t-octyl-3(benzotriazole-2-yl)phenyl!-methane PA1 Cyanamid UV 2098-2hydroxy-4-(2acrylocyloxy-ethoxy benzophenone! PA1 National S&C Permasorb MA-2 hydroxy-4-(2-hydroxy-3-methacryloxy) propoxy benzophenone! PA1 Cyanamid UV 24 2,2'dihydroxy4-methoxy benzophenone! PA1 BASF Uvinul 400 2,4-dihydroxy benzophenone! PA1 BASF Uvinul D49 2,2'-dihydroxy 4,4-dimethoxy benzophenone! PA1 BASF Uvinul D50 2,2',4,4'tetrahydroxy benzophenone! PA1 BASF Uvinul D35 ethyl-2-cyano-3,3 diphenyl acrylate! PA1 BASF Uvinul N-539 2-ethexyl-2-cyano-3,3-diphenyl acrylate! PA1 Ciba Geigy Tinuvin 213 PA1 Rhone-Poulenc Anti-UVP (Rhoidialux-P) PA1 2',2',4-trihydroxybenzophenone PA1 Uvinul M493.TM. from BASF, and commercially available mixtures thereof PA1 2-hydroxy-4-acryloyloxyethoxybenzophenone (polymer) PA1 2-hydroxy-4-acryloyloxyethoxybenzophenone PA1 4-hydroxy-4-methoxybenzophenone PA1 2-hydroxy-4-n-octoxybenzophenone PA1 (1) Improved impact strength of the structure, PA1 (2) Ability to hold photochromic dyes within the encapsulating interlayer material, PA1 (3) Ability to provide UV blocking characteristics by formulation of the interlayer, PA1 (4) Provision of good tintability by the coating itself.
In terms of case (1), applicants have found insurmountable obstacles occasioned by the chemical destruction of the dyes at the bath temperatures required to achieve a sufficient impregnation density in all ophthalmic hard resin materials, unless one utilises the techniques disclosed in Australian Patent Application PN 0071 "Method of Preparing Photochromic Article", the entire disclosure of which is incorporated herein by reference.
For case (2), applicants and others in the field have produced sample lenses which exhibit the photochromic effect. However, a lens coating must conform closely to the optical surface on which it is applied--and must adhere strongly in order to ensure product durability and to avoid deterioration over time. These two requirements limit both the thickness of a coating and the concentration of dye it can carry. Our experience is that insufficient change in lens transmission can be achieved by this approach. Coating thicknesses are in the range 2 to 4 .mu.m.
For case (3), there is indeed a viable method exploited commercially by Transitions Optical, Inc. (see for example U.S. Pat. No. 4,968,454 & U.S. Pat. No. 5,021,196) to achieve a satisfactory lens product. Dyes are incorporated, e.g. by imbibing beneath the lens surface furthest from the eye and the completed plastic element is coated with an abrasion resistant resin. This system however relies on the use of a specific lens material developed and sold by PPG Industries, Inc. (for example codes CR300-307 and CR407).
For case (4), many attempts have been made in the prior art to incorporate dyes in a variety of ophthalmic resins and thermopolymers. The technical issues to be overcome relate primarily to ensuring that the dyes are not destroyed by the initiators employed to cure a monomeric volume, producing a solid lens with optical integrity, or to ensure that a thermoplastic article can be formed at temperatures which have least detrimental effect on the dyes.
It is possible to achieve satisfactory results in casting lenses from tetraethylglycol dimethacrylate (U.S. Pat. No. 4,851,471 and U.S. Pat. No. 4,913,544) with a thermal cure system, in casting lenses from radiation curable systems (U.S. Pat. No. 4,912,185 & Application No 07/781392), and in thermal moulding of polycarbonate impregnated with photochromic dye stuff (U.S. Pat. No. 94/04225 and U.S. Pat. No. 94/04233). By modifying the chemistry of the monomer, Enichem Synthesis Spa have achieved a combined monomer/catalyst system which allows the incorporation of some selected organic dyes (including photochromic dyes) into a modified allyl diglycol carbonate (see U.S. Pat. Nos. 5,186,867 and 5,180,524). The catalyst employed is Luperox 231 from Elf-Atochem, which has no significant action on the families of organic molecules of interest. It has the chemical formula 1,1-Bis(t-butyl peroxy)-3,3,5-trimethylcyclohexane.
Applicants experience with conventionally known photochromic molecules incorporated into the lens is that both a desirable depth of darkening and a significant extension of fatigue life can be demonstrated. This is due, in part, to the reservoir of dye dispersed throughout the lens but is influenced also by the lower concentrations of oxygen and moisture within the bulk of the lens compared to near its surface. Both are known to accelerate fatigue of the photochromic dyes.
The lenses thus produced are found to be useful as sunglass lenses, but not as spectacle lenses with refractive power. This is because the optical density of an activated lens is greatest where the lens design causes the material thickness to be greatest. A refracting lens must, by definition, have bounding surfaces of different curvature. Thus its thickness will change according to the lens surface configurations to achieve the desired through power being provided. Furthermore, one surface--usually the front surface--may have localised curves or segments to provide multifocal or progressive addition for near vision. As a result of these physical design requirements, a so-called "body tinted" photochromic lens shows definite radial and local variations in colour density when activated.
These variations are unacceptable to a spectacle wearer on the grounds of utility and of cosmetic appearance. As noted above, the requirement for uniform depth of darkening can be met only when the lens containing the photochromic material is of uniform thickness. That is, when it has no power of refraction.